Friday, April 28, 2006

Posting has been light these last two weeks due to work-related travel. On the plus side, I got to attend the SPIE Defense and Security Symposium in Orlando, Florida, USA. Lots of good optics kit on exhibit, along with some very good presentations on the technical side.

Saturday, April 08, 2006

Microphone array beamforming is a subject that I have given a lot of my attention to over the last ten years or so. Simply put, microphone arrays are the electronic equivalent of a parabolic dish (those big plexiglass dishes that they use at football games to hear the sounds of contact and shouted calls on the field). Mic arrays let you hear sounds in a particular direction, possibly even far away, depending on the system design and environmental conditions.

As you might guess, I was pleased to learn last year that Microsoft will be building support for small arrays into Vista, its next generation version of Windows. The idea is that laptop and tablet PC manufacturers will embed small (4 element) mic arrays into their products to focus on the user's voice and cut down on noise so that VOIP, speech recognition, and other voice-based applications can work better. They also included an automatic echo canceller (AEC) to kill feedback loops between the microphone and loudspeaker in the laptop or tablet PC. These feedback loops are familiar to all who remember assemblies in gradeschool when the principal got his microphone too close to the loudspeaker and everyone got an earful of a high-pitched screeching tone! This would also happen on a VOIP call if the AEC wasn't included, so that is a good thing.

Anyway, I came across a introductory video clip from Microsoft Research on the topic of mic arrays and what is coming out in Vista. It can be found here. Note for Firefox users: you may need to use "Open in IE Tab" for the plug-in to play the video correctly.

Wednesday, April 05, 2006

The Washington Post reports on a study by researchers at UT-Austin (Texas, USA) that analyzed transcripts of President Bush, Vice President Cheney, Senator Kerry, and Senator Edwards on the campaign trail. The results may surprise you, especially if you are a US Democrat. Words do matter...

Seems strange that it apparently hasn't been done before, but Oculus Photonics has introduced the world's first UV camcorder, called the UVCorder(TM). The press release on Laboratorytalk says that it images in the 300-400nm range (near-UV band with peak at 370nm). The UV subsection of the system is actually a module that mounts on a visible light camcorder (both included as part of the system). The UV video is displayed on a 3.5 inch (8.9 cm) LCD.

Sounds pretty neat from the description, but seeing some images helps non-specialists understand why UV imaging is used in forensics. You can see some right now by going to their site and watching the Flash presention of visible and UV stills. Disappointingly, no video from the unit was posted on the site. They do list the main technical specifications, where it states that this particular Sony visible light camcorder uses Memory Stick for storing the images (still and AVI) and that it weighs 1.2 lbs (0.54 kg).

Tuesday, April 04, 2006

Researchers at Arizona State University (USA) have developed a thin liquid-crystal lens that can change refractive indexes (focusing powers) instantly. Assuming it makes a successful transition to the marketplace, this technology could improve the lives of millions of bifocal wearers. Links are here and here.

Sunday, April 02, 2006

Here is a writeup about research from Oxford University that was published in Current Biology on how the brain processes visual information, in particular what appears to be an assumption that it makes that works pretty well in the real world, but not in our developing computer-based virtual worlds (or "immersive reality" as it is called in the writeup).

I'll quote one portion that I particularly liked:

Commenting on the findings that people ignore the evidence of their own eyes, he cites Bayes, an eighteenth-century mathematician. ‘Bayes said that what we believe to be the state of the world is the product of two things: your prior assumptions and your sensory information. If your sensory information is very specific, you’ll go with that. But if it’s poor, or confusing, you’ll go with your prior assumption. That’s what seems to be happening here.’ In other words, the subjects’ belief that rooms stay the same size is so strong that it overrides all the usual cues from binocular disparity and motion parallax.

Sorry for the pun in the title, but a colleague of mine with a background in audio and video (!) often tells people that a good place to put one's money in the coming years is in hearing aid companies. The reason, he says, is that with the explosive growth of the personal music player market and how young people constantly turn the volume up past the point of hearing damage (or as he puts it, "where their ear drums are meeting in the middle of their heads"), today's youth are going to be needing hearing aids very early in their lives.

On that note (no pun intended this time), I am posting a link to the following news story about Apple putting a max volume limiter on some iPods.

Saturday, April 01, 2006

The Hindustan Times has a news report on a case currently in court where tampering with the video evidence was detected by a laboratory, including multiple edit points and discontinuities. The lab in this case was the Forensic Laboratory, Hyderabad.

In this case, the tampering appears to be pretty obvious, but it will likely only be a matter of time before such attempts become more sophisticated - and common. The forensic community has been looking at the issue of tampering detection for a while and various schemes have been devised to address the issue, including ones for protection (e.g. watermarking, cyclical redundancy checks or CRC, and time & date stamps) and for post-detection (e.g. automated tamper detection algorithms). It should be noted that no matter what protection schemes are implemented, they can not always be applied at the time that the evidence is originally recorded (e.g. evidence from a private citizen's answering machine recording or camcorder).

I personally believe that the idea of adding watermarking to original evidence needs to be examined carefully - watermarking, by its very nature, changes the evidence, which, as a general rule, should only be done when absolutely necessary. Additionally, even though the watermark is 'deeply buried' in the data, post-filtering algorithms could amplify the watermarking and create artifacts (which would sound like noise).

Let me be clear in saying that I am not taking the position that watermarking should not be done, but instead that if it is, then it should be done carefully and, if necessary, in a way that is reversible (for removal for filtering or validation purposes, for instance). Simply deploying a COTS (Commercial Off The Shelf) solution from the music industry should not be seen as a shortcut way for a laboratory to make its evidence tamper-proof.